1. Field of the Invention
The invention relates to a device to be used by optometry or optical workers to apply a gradation of tint density to plastic or other materials for optical or ophthalmic lenses. This is desirable since the amount of light entering from above is typically greater than that entering from horizontally or below, hence a greater tint density in the upper portion of the lens will reduce glare. Applying gradations of tint density by optical laboratory workers to lenses has been a common practice.
2. Description of Related Art
Many gradient tinting devices have been used in the past to create gradations of tint density on plastic ophthalmic lenses. In January of 1981, Brain Power Incorporated's Dr. Herbert Wertheim and Dr. Philip Bartick introduced the BPI Computer Gradient, a microprocessor controlled stepper motor powered system, which lowered the lens into a heated bath containing water based tint. Elias and Chika in 1990 (U.S. Pat. No. 4,915,986) patented a similar device. In 1987, Suter (U.S. Pat. No. 4,710,199) described a tinting system which applied ultrasonic energy to the tint bath in order to agitate the fluid and produce a more uniform solid or gradient tinted lens. In 1993, Chika and Elias (U.S. Pat. No. 5,201,955) described a device for producing an annular gradation of tint density on a plastic ophthalmic lens by vertically reciprocating the lens in and out of a tint bath while rotating the lens about an axis central to and orthogonal to the plane of the lens.